The subject matter disclosed herein relates to a multi-rotor helical compressor. In particular, the subject matter disclosed herein relates to a multi-rotor compressor that is configurable to receive interchangeable planet rotors to provide manufacturing flexibility in assembling compressors having different capacities.
Screw type compressors are a type of compressor used for the compression of gases such as air or refrigerant. In general, the screw compressor rotates one or more rotors having a helical shape within a cavity. As the gas enters the inlet of the cavity, the gas is drawn by the rotating helical shape and compressed by the reduction in the cavity volume. The compressed gas is then discharged through the outlet of the compressor.
One type of compressor, typically referred to as a twin-screw compressor comprises a pair parallel interacting rotors. The rotors are connected by a gear arrangement coupled to a driving motor. The rotors are comprised of helical lobes affixed to a front and rear shaft. One rotor is called the male rotor and the other rotor is the female rotor. The male rotor has bulbous lobes that interact with valleys formed in the female rotor. The valleys are sized to match the curvature of the male lobes. In a typical twin screw compressor, the female rotor will have five valleys and the male rotor has three lobes. With this combination, the male rotor turns 1.66 times to every one time of the female rotor. It should be appreciated that the number of lobes on the male and female rotor will vary from one compressor manufacturer to another. However, the female rotor will typically have numerically more valleys than the male rotor has lobes.
Another type of multi-rotor compressor utilizes a center or “sun” rotor that interacts with two or more parallel “planet” rotors. As with the twin screw compressor, the multi-rotor compressor has both male and female rotors. Systems have been proposed with the sun rotor being either the male or the female rotor. Where the sun rotor is the male rotor, the corresponding planet rotors have a female profile and vise versa. During operation, the compressor motor only drives the sun rotor. The planet rotors are driven by the rotation of the sun rotor through the working fluid or gas being compressed.
Both the sun rotor and the planet rotors are enclosed within a housing. The housing typically includes bores that are formed in a casing to receive the shafts for the sun rotor and planet rotor. The bores provide an axis of rotation for the rotors. While this arrangement works suitably, each compressor size, in terms of output, requires a new design with a different configuration or rotors, rotor lobes, rotor valleys and the like.
While existing multi-rotor compressors are suitable for their intended purposes, there still remains a need for improvements particularly regarding the scalability of the compressor while improving manufacturability of the multi-rotor compressors to minimize manufacturing and assembly costs.